The upper and lower rams of a rotary press, which are movable by strokes within a ram guide and interact with bores in the die table, are controlled in height during the rotation of the rotor. The bores are filled with a powder, which requires compaction, by means of a filling device where the lower rams remain inside the bore while the upper rams are above the bore. The filling volume is predetermined by the height positions of the lower rams while filling is done. After compaction, the compacts are thrown out onto the level of the die table, which includes an ejector cam. For an adjustment of the filling volume, the lower rams are pulled down to the filling depth needed in the bore by means of a charging cam. After the filling procedure, the lower rams are moved upwards again by a certain degree in a proportioning station, which causes some fraction of the charge to be batched out, i.e. returned to the filling device. To this effect, a proportioning cam is provided which is infinitely variable in height by means of an appropriate, regulated positioning drive.
Usually, the individual cams are implemented by cam elements which guide the ram heads. This is also the case for the charging cam. It is known to provide charging cams having different filling height stages. If a major filling volume is necessary a charging cam of a major adjustable depth is chosen, and vice versa. The accurate filling volume is set by a more or less large stroke of the proportioning cam. If the batching-out strokes of the proportioning cam are large it might happen that powder which was proportioned back to the filling device leads to problems in filling, e.g. because of clogging, undesirable compression of the powder within the filling device, lumping of the powder, etc. In such cases, it might be necessary to exchange the charging cam against a more suitable one, e.g. one of a smaller filling depth.
A change-over to another charging cam possibly may also be required if the tablet output of the machine is increased. It has turned out that if the position of the lower rams remains the same the material volume loaded into the bores is the smaller the higher is the speed of the rotor From a certain circumferential speed onwards, the remaining filling time is too small for filling up the bore with powder completely. The consequence is that a precise filling volume can no longer be achieved by batching out material in the proportioning station. Also here, it may be necessary to vary the filling depth, i.e. increase it here, in order to give the compact its desired weight.
Exchanging a charging cam involves a great expenditure in both assembly and time. For this purpose, it is necessary to dismount the machine cladding elements and remove the powder filling device from the machine. It further requires the disassembly of several lower rams and drawing off the powder that is in the press. The production process of the press naturally is disrupted during the resetting period.
It is the object of the invention to provide a device for the guidance of lower rams across their lower-ram heads in a rotor-type rotary press in the area of a filling device which remedies the disadvantages described and allows varying the filling depth with no major expenditure.